In the production of nonwoven webs from synthetic resin strands it is customary to deposit the strands so that they intermingle upon a roving surface, usually a conveyor belt which is foraminous, i.e. permeable to a gas and below which a suction may be applied to assist in the formation of the web of intermingled strands. The web is conveyed away from the site at which it is formed on the conveyor belt and may be subject to further processing, such as calendering between at least one pair of rolls after the web has been removed or discharged from the belt.
The strands which form the web or fleece are synthetic resin threads which can be continuous or discontinuous. A continuous synthetic resin thread can be a continuous thermoplastic synthetic resin filament extruded from a spinneret. The strands may also be discrete fibers, i.e. extruded filaments which are subdivided upon forming. In general the webs can be formed by either the spun-bond process from such continuous filaments or by the melt-blown process from short fibers and are frequently referred to as mats or fleeces. The products made by the melt-blown and spun-bond processes may be used as sanitary pads, diapers, disposable hygienic garments and the like or as fabrics to be impregnated with synthetic resin or other materials as reinforcements for structural layers or as liners or supports for a variety of finished products.
As a general matter, the foraminous belt, also referred to a sieve belt or a suction belt since a suction is often drawn from below the belt for deposit of the web, receives the unconsolidated mass of intermingled strands. The strands may be hot and thus may fuse together at contact points or crossing points and may consolidate somewhat on cooling. In general, however, the more or less unconsolidated fleece or web is carried by the belt over a rerouting roller at which the belt is deflected from its upper pass to a return pass and the web, no longer supported by the belt, is withdrawn therefrom. The removal of the web from the belt sometimes requires the application of a longitudinal force to the web, this force being applied by the processing equipment downstream of the rerouting roller at the end of the upper pass of the belt. This force may be excessive and, especially with high speeds of web formation and transfer or reduced area weight (weight of the web per unit area) and web density, the forces which may be applied to the web at the discharge end of the conveyor can result in damage to the web, reduction in web quality, a varying transverse contraction of the web and injury to the edges of the web. In extreme cases the web may be torn and damage of this type can give rise to interruption in the web-producing process, especially if the web tends to be entrained onto the return pass of the belt.